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Discussion Starter #1
This has been bugging me for a while now. For about a year I have intermittently been getting the CEL light coming on, often after filling up with gas. I was able to tighten the gas cap and start the engine three times to get it to go away for a while.

Then I got a new gas cap from the dealer a few weeks ago and I didn't get a CEL for awhile. I thought I had licked the problem.

However, recently, I got a CEL and went to Autozone to get the codes read. It returned multiple codes:
P0463 (Fuel level sensor circuit high input)
P0447 (Evaporative emission system-purge vent solenoid Circuit condition)
P1400 (Fuel tank pressure control solenoid low input)
After re-setting the codes, the CEL came on immediately.

I searched online about the codes and am concerned that it might be a connector issue behind the wheels. I looked up the service procedure for checking it and it seemed challenging (remove back seat, etc) for someone who doesn't work on cars regularly -- i.e. me.

About a week ago, the CEL went out without me doing anything and it is still out. But I'm going on a long trip soon (headed to Colorado) and I don't want any issues during the trip.

I have had the battery checked at two places (Autozone and Les Schwab) and it checked out fine at both places. It's the OEM battery and I have 66.7K miles on the car.

Any other suggestions to try before I begin taking out the back seat and digging for wires and connectors?

Thanks in advance...
 

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A few notes raised by your description:

If a problem is detected by the OBD system and the CEL is turned on, after which the problem disappears, the CEL will remain on for 3 consecutive driving cycles without any problem being detected and then will go out automatically. Also, even if the CEL goes out automatically, the code or codes that caused the light to be turned on will be stored in memory for up to 40 driving cycles.

Your experience with the light going out on it's own seems to be consistent with this. In addition, the three codes that were found could actually be one code that triggered the CEL that was on at that time, but also two codes that were registered some time earlier but aren't an actual problem at the present time. Thus the importance of reading the codes whenever the light comes on -- best to know what it was, even if the light goes out.

This leads to the question -- if the codes were manually cleared using the code reader it's likely they were also erased from memory. If the CEL came on immediately after, were the codes read again to see which one or ones caused the immediate re-appearance of the CEL? That might have helped narrow down the possibilities. (Code readers are relatively inexpensive -- recently there was a basic one on e-Bay for less than $20. Also, you can identify the codes without a separate code reader following the procedure in this thread: http://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/19053-05-09-how-read-diagnostic-trouble-codes-dtcs.html

The P0463 can be caused by a bad connection to the fuel level sensors in the tank, but if that were to happen, I would think the fuel gauge would also malfunction. Was there any evidence of this, e.g., gauge at full or empty end when it shouldn't be, or the Low Fuel light being on?

The fuel level sensors, fuel tank pressure solenoid and vent solenoid do seem to share a common harness connector (R46), so your focus on that connector (under the seat) is logical. But the likelihood of it being faulty (loose, intermittent connection) seems, to me, to be low unless that area of the car was worked on at some time, e.g. body work, or detailing/cleaning in the rear seat area.

Interesting combination of codes that I don't recall reading about at the same time before. Fortunately, as far as I know, none causes the car to shut down or go into a failsafe condition that will prevent it from being driven normally, although emissions might suffer, and as noted, the fuel gauge might be strange.

Not sure if this helps. Hope you will keep us informed.
 

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Discussion Starter #3
Plain OM,
Thanks for your thoughtful response.
Some answers:

If the CEL came on immediately after, were the codes read again to see which one or ones caused the immediate re-appearance of the CEL?
No, the clerk had gone back in to the store as I was pulling out. I think your observation about getting a code reader and reading them immediately is the right approach.

The P0463 can be caused by a bad connection to the fuel level sensors in the tank, but if that were to happen, I would think the fuel gauge would also malfunction. Was there any evidence of this, e.g., gauge at full or empty end when it shouldn't be, or the Low Fuel light being on?
The initial time I had a CEL come on the gas gauge did malfunction and the low fuel indicator came on with the needle at "E". That hasn't happened since.

I am starting my search for a code reader now. Thanks
 

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The initial time I had a CEL come on the gas gauge did malfunction and the low fuel indicator came on with the needle at "E". That hasn't happened since.
That is consistent with an open circuit in the wiring connection to the fuel level sensors which is what the P0743 is indicating.

Let us know what you find . . .
 

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Discussion Starter #6
I pulled the trigger and purchased the code reader (Autel MaxiScan) recommended in this thread.


Replace the Battery.

Then check the alternator output with the new battery.
Cardoc,
after the gas cap, the battery going bad was my next assumption. However, I had it tested at two places and both gave it a passing grade.

I'd prefer not to replace unless needed, but perhaps I should bite the bullet since it is 6 years old.
 

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Discussion Starter #7
Thought I'd update this thread since it's a few months old...

I bought a code reader and have been getting the same three codes occasionally and have become adept at doing the re-set.

Since the problem wasn't going away, I finally decided to buy a new battery, as had been suggested. I wasn't having any other battery issues, but decided since the OEM battery was 6+ years old, it was about time.

I'll provide an update if I see any CEL codes.
 

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Sounds like mice or a water problem that is causing connectivity issue in that harness.

Tom
 

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Sounds like mice or a water problem that is causing connectivity issue in that harness.

Tom
If I keep getting the codes, that will be my next area of investigation. I have had mice issues before in the cabin air filter, so it wouldn't surprise me too much if they were the culprits.
 

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Discussion Starter #10
My saga continues. I replaced the battery, but lately have been getting the CEL light again. P0447 is the code, so I'm going to start troubleshooting the associated harness as recommended in other P0447 threads.
 

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In addition to the connectors under the rear seat, there's another large connector, B97, that seems to also be used by both the drain valve wiring and the fuel gauge wiring. I believe it's located in the left side of the dashboard area (underneath) or in the "kick panel" area (to the left of the driver left foot rest. It's a 20 pin connector, in two rows.

Of course, as was noted, it might be something like a chewed-through wire harness, and not a loose/bad connector. Looks as if you're into some detective work . . .

Let us know how it goes . . .
 
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